Obama, looking tired and strained after the gruelling presidential campaign, said: "I do not underestimate the enormity of the task.

Barack Obama last night promised to do all in his power to drag America out of the financial doldrums as he gave his first speech since the election.

And he did his best to damp down the euphoria of his victory by warning of tough times ahead.

Obama, looking tired and strained after the gruelling presidential campaign, said: "I do not underestimate the enormity of the task.

"Some of the choices we make will be difficult. It is not going to be quick, it is not going to be easy for us to dig ourselves out of the hole we are in.

"But America is a strong and resilient country and I know we will succeed if we put aside partisanship and politics and work together as one nation. That's what I intend to do.

"A new president can do an enormous amount. I'm confident that a new president can have an enormous impact.

That's why I ran for president."

Obama, who becomes America's first black president when he takes over from George W Bush on January 20, told the Chicago news conference the US was facing the "greatest economic challenge of our lifetime".

He said the US needed a rescue plan for the middle class, further extension of unemployment benefits and help for the struggling car industries.

And he insisted his key priorities such as healthcare and energy policy could not be put on hold.

Obama, who was flanked by his new White House chief of staff Rahm Emanuel and vice president-elect Joe Biden, will meet President George Bush on Monday for talks on key issues such as the war and the economy.

He admitted there were likely to be differences of opinion but said: "Now's a good time for us to set politics aside for a while and think practically about what will actually work to move the economy forward.

"It's in that spirit that I will have the conversation with the president."

On a lighter note, Mr Obama was asked about his election night promise to get daughters Malia, 10, and Sasha, seven, a new puppy when they moved into the White House. He told reporters this was a "major issue".

Obama said his preference was for a dog from a rescue shelter. He added: "But a lot of them are mutts, like me."